A logic unit of a motor driving device consumes a greater amount of power as a circuit size thereof is increased. Further, a brushless motor driving device capable of reducing standby power of a logic unit by cutting off power supply to the logic unit when an operation of a motor is stopped is known.
However, if the power being supplied to the logic unit is cut off when the operation of the motor is stopped, the logic unit stops working, and thus, conduction of the motor cannot be controlled and a signal for detecting the revolutions per minute (RPM) of the motor cannot be generated as well. For these reasons, for example, even though an outdoor fan of an air-conditioner continues to be rotated by receiving wind even when power is not being supplied to the motor, the rotation of the outdoor fan cannot be recognized.